HK1108135B - Hydrophilizing agent for hydrophobic porous membrane, and method for hydrophilizing hydrophobic porous membrane and test method using this agent - Google Patents

Description

Hydrophilizing agent for hydrophobic porous membrane, method for hydrophilizing hydrophobic porous membrane using same, and method for detection

Technical Field

The present invention relates to a hydrophilizing agent for a hydrophobic porous film, which contains a low-foaming surfactant. In particular, the present invention relates to the use of a hydrophobic porous membrane such as a microfiltration membrane or an ultrafiltration membrane in a hydrophilization treatment of the hydrophobic porous membrane.

Background

Porous membranes such as microfiltration membranes and ultrafiltration membranes are widely used in various fields because they are used for treatment of contaminated materials such as industrial wastewater, sterilization of water for pharmaceuticals, and the like. The membrane to be used may be roughly a hydrophobic porous membrane or a hydrophilic porous membrane, but in the field of solid-liquid separation, a hydrophobic porous membrane is preferably used from the viewpoints of chemical resistance, stain resistance, weather resistance, oxidation deterioration resistance and the like. However, since the hydrophobic porous membrane has hydrophobicity, water or an aqueous solution cannot directly pass through pores of the hydrophobic porous membrane, and even if it can pass through the pores, a considerable pressure must be applied. Therefore, hydrophilization treatment is performed on the hydrophobic porous film in advance to allow water or an aqueous solution to easily pass therethrough. The hydrophilization treatment is required not only for the first use after the production of the hydrophobic porous film but also for the drying of the hydrophobic porous film by contacting a part or the whole of the hydrophobic porous film with air during the inspection, cleaning and long-term shutdown of the hydrophobic porous film. In particular, a hydrophobic porous membrane made of a highly hydrophobic polymer such as a fluororesin has a remarkably lowered liquid permeability upon drying, and therefore, it is necessary to appropriately hydrophilize the hydrophobic porous membrane.

As a method for hydrophilizing such a hydrophobic porous film, for example, a method of introducing a hydrophilic group into the film itself (patent document 1), or a method of treating the film with deaerated water (patent document 2), alcohol (patent document 3), glycerin (patent document 4), and an inorganic salt (patent document 5) are known.

However, in the method of introducing a hydrophilic group into the membrane itself (patent document 1), in order to remove the unreacted monomer constituting the hydrophilic group remaining on the membrane, it is necessary to sufficiently clean the membrane with a cleaning liquid such as a large amount of water. In the method of treating a membrane with deaerated water (patent document 2), it is essentially necessary to pressurize the deaerated water to pass through the membrane, which makes the treatment method complicated. Further, since the hydrophilized film must be kept in a wet state at all times, handling is inconvenient because the module containing the hydrophilized film is filled with a wetting liquid or the like during transportation, and sale. In the methods of treating a membrane with an alcohol or the like (patent documents 3 to 5), the alcohol or the like used for the treatment remains in the hydrophobic porous membrane, and therefore, it is necessary to sufficiently clean the membrane with a large amount of a cleaning liquid when the membrane is used.

As another hydrophilization treatment method for a hydrophobic porous film, a method of treating a film with a surfactant by a specific method has also been proposed (patent document 6).

However, in patent document 6, when the film is treated with the surfactant, there is a disadvantage that the film is gradually eluted into the treated water due to the residual surfactant, and in order to treat the film with the surfactant, it is necessary to use a specific method of patent document 6 to reduce the amount of the surfactant used and suppress the elution. That is, patent document 6 merely reduces the amount of the surfactant to be used and the amount of the surfactant to be eluted, but does not solve the problem of the elution of the surfactant at all.

Patent document 1: japanese unexamined patent publication No. 6-296686

Patent document 2: japanese patent laid-open No. Hei 5-208121

Patent document 3: japanese patent laid-open No. Sho 58-96633

Patent document 4: japanese patent laid-open publication No. 2002-95939

Patent document 5: japanese patent laid-open No. 6-277470

Patent document 6: japanese patent laid-open No. Hei 1-119310

Disclosure of Invention

A first object of the present invention is to provide: a hydrophilizing agent suitable for hydrophilizing a hydrophobic porous film and a hydrophilizing method using the same.

A second object of the present invention is to provide: a hydrophilizing agent which is used for hydrophilizing a porous hydrophobic film, can minimize the amount of the hydrophilizing agent remaining after the hydrophobic porous film treatment, and can easily remove the remaining hydrophilizing agent, and a hydrophilizing method using the hydrophilizing agent.

A third object of the present invention is to provide: a method for detecting a membrane module, which can detect a leakage, a defective product, a clogging or the like of a membrane module comprising a hydrophobic porous membrane, by detecting a hydrophilizing agent impregnated in the membrane module, and which can preferably suppress the generation of air bubbles in the hydrophilizing agent.

A fourth object of the present invention is to provide: a preferable method of performing hydrophilization treatment by directly immersing a membrane module containing a hydrophobic porous membrane in a liquid to be treated (liquid to be treated) in a membrane separation tank containing the liquid to be treated and provided with an aerator.

The present inventors have intensively studied to solve the above problems, and as a result, they have found that the above problems can be solved by using a specific low-foaming surfactant having defoaming properties and low surface tension, and have completed the present invention.

Namely, the present invention:

1. disclosed is a hydrophilizing agent for a hydrophobic porous film, which is characterized by containing a surfactant which is an vicinal alkyne diol, an ethoxylate of the vicinal alkyne diol, or a mixture thereof, and which has a foaming property wherein a foam height immediately after foaming of an aqueous solution of the surfactant of 0.1 mass% at 25 ℃ measured by a Ross-miles method according to JIS K3362 is 40mm or less.

2. A method for hydrophilizing a hydrophobic porous film, which comprises the step of bringing the hydrophobic porous film into contact with the hydrophilizing agent for a hydrophobic porous film as described in the above item 1.

3. The method for hydrophilizing a hydrophobic porous film according to claim 2, further comprising a step of drying the hydrophobic porous film which has been brought into contact with the hydrophilizing agent for a hydrophobic porous film according to claim 1.

4. A method for detecting a membrane module having a main body, an inlet and an outlet provided in the main body, and a hydrophobic porous membrane provided in the main body, comprising the steps of:

(1) a step of immersing the membrane module in the hydrophilizing agent for a hydrophobic porous membrane described in the above 1;

(2) introducing a detection gas from the inlet, passing through the porous hydrophobic film, and discharging the gas from the outlet; and

(3) and observing the air bubbles discharged from the membrane module.

5. A method for testing and hydrophilizing a membrane module having a main body, an inlet and an outlet provided in the main body, and a hydrophobic porous membrane provided in the main body, the method comprising the steps of:

(1) a step of immersing the membrane module in the hydrophilizing agent for a hydrophobic porous membrane described in the above 1;

(2) introducing a detection gas from the inlet, passing the detection gas through the porous hydrophobic membrane, and discharging the detection gas from the outlet;

(3) observing the gas bubbles discharged from the membrane module; and

(4) and drying the membrane module.

By immersing and drying a highly hydrophobic membrane such as a fluorine-based separation membrane in the low-foaming surfactant of the present invention for a certain period of time, an excellent hydrophobic porous membrane can be provided which can be stored stably in a dry state without being deteriorated for a long period of time, can be spontaneously and completely wetted with water when used, can be stored easily in a dry state, and does not require a pretreatment when used.

Further, the method for hydrophilizing a porous hydrophobic membrane of the present invention can easily and smoothly restore good liquid permeability to a porous membrane which becomes hydrophobic after drying at low cost with a small amount of chemicals, labor and time, and is extremely advantageous for industrial applications.

Drawings

FIG. 1 is a schematic configuration diagram of an example of the hydrophilization treatment method of a membrane suitable for the present invention.

Description of the symbols

1 Membrane separation tank

2 Membrane module

3 liquid to be treated

4 air diffusing pipe

5 piping

Detailed Description

(1) Hydrophilizing agent for hydrophobic porous film

The hydrophilizing agent for a hydrophobic porous film of the present invention contains a low-foaming surfactant, an optional solvent, and an optional additive.

(1-1) surfactant

The surfactants of the present invention have low foaming properties. The foaming property was measured according to the Rossilies method (JIS K3362). For example, the foaming ratio immediately after foaming and the foaming ratio 5 minutes after foaming are measured by the Rossilies method (JIS K3362) using a foaming ratio measuring apparatus according to JIS K3362 at 25 ℃ using a 0.1 mass% aqueous surfactant solution. The Rossmiles method here is: 50ml of an aqueous surfactant solution was charged into a glass cylinder having an inner diameter of 50mm, 200ml of the aqueous surfactant solution was dropped from a height of 90cm for 30 seconds, and the height (mm) of the foam immediately after the dropping and after a certain period of time was measured. The surfactant of the present invention preferably has a foam height of 40mm or less, more preferably 30mm or less, and still more preferably 20mm or less immediately after foaming as measured by the aforementioned Rossmiles method. When the particle diameter is 40mm or less, foaming by the surfactant can be suppressed to a low level, and therefore, it is preferable. The surfactant of the present invention preferably has a foam height of 20mm or less, more preferably 15mm or less, and still more preferably 0 to 10mm, as measured by the Rossilies method, after foaming for 5 minutes. When the particle diameter is 20mm or less, foaming by the surfactant can be suppressed to a low level, and therefore, it is preferable.

The static surface tension (room temperature) of a 0.1 mass% aqueous solution of the surfactant used in the present invention is preferably 29mN/m or less. More preferably not more than 28mN/m, and particularly preferably in the range of 20 to 28 mN/m. The static surface tension can be measured by the method of JIS Williamsy (plate) (ウイルヘルミ (プレ ℃ C. -. ト)) using an automatic surface tension meter CBVP-Z (manufactured by Kyowa interface science Co., Ltd.). When the static surface tension is 30mN/m or less, the hydrophobic film tends to be hydrophilized in a short time, and therefore, the static surface tension is preferable.

Further, the dynamic surface tension (room temperature) of a 0.1 mass% aqueous solution of the surfactant used in the present invention is preferably 50mN/m or less. More preferably 10 to 50mN/m, and particularly preferably 25 to 40 mN/m. The dynamic surface tension can be measured from values at 1Hz and 10Hz of a 0.1 mass% aqueous solution using, for example, a bubble pressure type dynamic surface tension meter KRUSS BP-2 (manufactured by KRUSS).

The surfactant that can be used in the present invention is selected from anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants. The nonionic surfactant is particularly preferable from the viewpoint of less foaming and foaming.

Specific examples of the nonionic surfactant include ethers such as an Acetylene glycol surfactant, an Acetylene alcohol (Acetylene alcohol) surfactant, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene alkylallyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, and polyoxyethylene alkenyl ether (ポリオキシアルキレンアルキルエ - テル); esters such as polyoxyethylene oleic acid, polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, and polyoxyethylene stearate; silicon-based surfactants such as dimethylpolysiloxane; and other fluorine-containing surfactants such as fluoroalkyl esters and perfluoroalkyl carboxylates.

Among the above nonionic surfactants, the acetylene glycol-o-group surfactant is preferable because it has excellent wettability, permeability and defoaming property. The alkyne o-glycol surfactant is a relatively stable substance and has a characteristic that the membrane is not spoiled by organisms when being stored for a long time. Particularly, the alkyne-o-diol surfactant has characteristics such as low dynamic surface tension and high permeability. Therefore, it has effects of being suitable for hydrophilization treatment of a thick hollow fiber membrane, short treatment time, and the like.

Specific examples of the alkyne-vicinal diol surfactant include 2, 4, 7, 9-tetramethyl-5-decyne-4, 7-diol, 3, 6-dimethyl-4-octyne-3, 6-diol, 3, 5-dimethyl-1-hexyne-3-ol, 2, 5, 8, 11-tetramethyl-6-dodecyne-5, 8-diol, and an ethoxylate of the above.

If necessary, 1 or more of them may be appropriately selected and used, and the total number of moles of ethylene oxide added to the ethoxylate is preferably in the range of 2 to 30 moles. More preferably in the range of 4 to 12 moles. The total number of moles of ethylene oxide added is 30 moles or less, whereby static and dynamic surface tensions can be reduced, and the composition is suitable for use as a hydrophilizing agent.

Commercially available Products of the alkyne vicinal diol surfactant and the ethoxylate include, for example, Surfynol104, 82, 465 and TG manufactured by Air Products, and Olifin STG, Olfin E1010, Olfin EXP4036 and Olfin PD-001 manufactured by Nissan chemical Co.

For example, the static surface tension of 0.1 wt% of 1 kind of the alkyne vicinal diol surfactant, Olfin EXP4036 (manufactured by riken chemical industries, inc.) was shown to be 30mN/m or less. As for Olifin PD-001. Olfin STG (both manufactured by Nissan chemical industries Co., Ltd.), a static surface tension of 0.1 wt% was 30mN/m or less. Thus, the alkyne vicinal diol surfactant can exhibit good hydrophilicity at an extremely low concentration.

(1-2) solvent

As the solvent for dissolving the surfactant of the present invention, water, an aqueous solution containing an electrolyte such as physiological saline, a lower alcohol having 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms such as ethanol or methanol, pyridine, chloroform, cyclohexane, ethyl acetate or toluene, or a mixed solvent thereof can be used. In particular, water is preferably used from the viewpoints of the influence on hydrophilizing treatment materials, post-treatment with solvents, safety, cost, and the like. The water used is preferably water obtained by filtering ordinary tap water or ion-exchanged water with a hollow membrane having a pore diameter of 0.01 to 1 μm.

(1-3) additives

The hydrophilizing agent for a hydrophobic porous film of the present invention may contain any additive. Examples of additives that can be used include surfactants other than those described above, glycerin, and the like.

For example, in order to improve the solubility of the surfactant used in the present invention in water, ethylene oxide or propylene oxide or a mixture thereof, or a polymer composed of a block copolymer thereof (for example, Epan750, manufactured by first Industrial pharmaceutical Co., Ltd.) may be used.

They may be used in a range not impairing the properties of the hydrophilizing agent of the present invention, and for example, the whole amount of the hydrophilizing agent may be used in a range of 5 to 90% by mass, and more preferably 5 to 50% by mass. In addition, pure water or a water-soluble organic solvent may be used within a range not impairing the properties of the hydrophilizing agent of the present invention, and for example, 25 mass% or less, more preferably 10 to 20 mass% of the whole hydrophilizing agent may be used.

(1-4) preparation of hydrophilizing agent for hydrophobic porous Membrane

The hydrophilizing agent for hydrophobic porous films of the present invention can be prepared by directly dissolving the surfactant, or the surfactant and any additives in a solvent. As a method for dissolving the surfactant, a method of mixing by a known mixing preparation method such as a propeller mixer is exemplified. The solid components at room temperature may be mixed after heating as necessary.

The hydrophilizing agent for a hydrophobic porous film of the present invention contains the surfactant in an amount of 0.05 to 5% by mass, preferably 0.05 to 1% by mass, based on the whole hydrophilizing agent for a hydrophobic porous film. When the surfactant content is 0.05% by mass or more, excellent properties as a hydrophilizing agent can be imparted. When the surfactant content is 5% by mass or less, the amount of elution from the membrane can be reduced, and the COD can be reduced.

(2) Membrane module

The hydrophilizing agent for a hydrophobic porous membrane of the present invention is used for hydrophilizing a hydrophobic porous membrane in a membrane module. As the membrane module, various membrane modules such as a flat membrane module, a cylindrical membrane module, a pleated membrane module, and a hollow fiber module can be used.

(2-1) Structure of Membrane Module

The membrane module has a body, an inlet, an outlet, and a porous membrane. Specifically, the membrane module body is provided with an inlet and an outlet, and a porous membrane is provided inside the membrane module body. The inlet and the outlet may be provided at both end portions of the main body (linear two-port type), and either one of the inlet and the outlet may be opened largely (linear one-side opening type). A porous membrane is connected to the interior of the body, dividing the body into a 1 st chamber having an inlet and a 2 nd chamber having an outlet. The attaching includes adhering or enclosing an end of the porous membrane to an inner wall of the body, or detachably attaching an end of the porous membrane to an inner wall of the body. Therefore, the membrane module of the present invention has a structure in which liquid and gas introduced from an inlet are introduced into a main body, pass through a porous membrane at all times, and are discharged from an outlet.

In addition, the inlet, outlet and main body of the membrane module of the present invention may be made of stainless steel, steel or other metals; fluororesin, ABS resin, polyolefin resin, vinyl chloride resin, and the like.

(2-2) hydrophobic porous Membrane

Any porous membrane may be used as the hydrophobic porous membrane of the present invention as long as it has hydrophobicity. Examples of the shape of the hydrophobic porous membrane of the present invention include a flat membrane, a hollow fiber membrane, a tubular membrane, and a spiral membrane. The hydrophobic porous membrane of the present invention may be a separation membrane such as a microfiltration Membrane (MF), an ultrafiltration membrane (UF) or a nanofiltration membrane (NF).

The hydrophobic porous membrane of the present invention may be formed of any of various materials as long as it can be formed into a separation membrane, for example, cellulose, polyolefin, polyvinyl alcohol, polysulfone, polyacrylonitrile, fluorine resin, or the like. Examples thereof include polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polysulfone, and the like. In particular, as the surface characteristics of the hydrophobic porous film, a resin having high hydrophobicity is preferably used, and a fluororesin is particularly preferable. Among the fluororesins, vinylidene fluoride resins are more preferable from the viewpoint of the formability and chemical resistance of the film. The vinylidene fluoride resin herein includes, in addition to a homopolymer of vinylidene fluoride, a copolymer of vinylidene fluoride and a comonomer capable of copolymerizing with vinylidene fluoride. Examples of the copolymerizable monomer include vinyl fluoride, tetrafluoroethylene, trifluoroethylene, and hexafluoropropylene.

The hydrophobic porous membrane of the present invention has a plurality of pores. The pores are preferably continuous pores penetrating the surface and back surface of the hydrophobic porous membrane. The pore diameter of the fine pores can be arbitrarily selected according to the purpose, and is, for example, in the range of 0.01 to 5 μm, preferably 0.1 to 1 μm. The hydrophobic porous film of the present invention is: an asymmetric structure in which the surface pore diameter of one side of the hydrophobic porous membrane is small and the surface pore diameter of the other side is large is preferable. In the case of the asymmetric structure, the pore diameter of the surface on one side is more than 1 time and 100 times or less, preferably 2 to 10 times larger than that of the surface on the other side.

When the hydrophobic porous membrane is a hollow fiber membrane, the outer diameter of the hollow fiber is, for example, 0.1 to 10mm, preferably 0.5 to 5 mm. The hydrophobic porous film of the present invention has a pure water permeability coefficient of 10 to 250m, which indicates the liquid permeability to pure water³/m²A pressure of/hr/MPa, preferably 20 to 150m³/m²The pressure is/hr/MPa. The pure water permeability coefficient can be obtained by the following equation.

Pure water permeability coefficient [ pure water permeability (m)³)]/[ surface area of porous film (m)²)]/[ permeation time (hr)]/[ pressure of pure Water (MPa)]

(3) Hydrophilization method for hydrophobic porous membrane

In general, when the hydrophobic porous membrane is used for the first time, such as when the porous membrane, an exchange membrane, a membrane washed with a chemical, or when the membrane is not used for a long time, the membrane surface comes into contact with air and becomes dry. In this case, even if the membrane is immersed in a liquid to be treated (a liquid to be treated) or the like again to filter the liquid to be treated, the liquid permeability is deteriorated and the original function of the separation membrane cannot be exhibited. Therefore, the pores of the hydrophobic porous membrane are hydrophilized, and then the liquid to be treated passes through the pores, whereby the liquid permeability can be improved and the membrane can be made to have good contamination resistance. In addition, from the viewpoint of eliminating the inefficient operation of collecting the liquid to be treated as a waste liquid and enabling the use of the hydrophobic porous membrane as soon as possible, it is preferable that the hydrophilizing agent is removed immediately when the liquid passes through the hydrophobic porous membrane.

Hydrophilization of the hydrophobic porous film includes a step of bringing the hydrophobic porous film into contact with the hydrophilizing agent for the hydrophobic porous film. Hydrophilization of the hydrophobic porous membrane in the membrane module will be described below.

The hydrophilization treatment using the hydrophobic porous membrane of the present invention in the membrane module is performed by injecting the hydrophilizing agent for the hydrophobic porous membrane from the side of the hydrophobic porous membrane facing the 2 nd chamber having the outlet. When there are 2 or more outlets, (a) the hydrophilizing agent for the hydrophobic porous film may be injected from all the outlets, or (b) the hydrophilizing agent for the hydrophobic porous film is injected from at least 1 or more outlet, and the remaining hydrophilizing agent for the hydrophobic porous film is discharged from the remaining outlets.

(a) When the hydrophilizing agent for the hydrophobic porous membrane is injected from all the outlets, the gas retained in the outlet and the 2 nd chamber having the outlet is pushed toward the 1 st chamber having the inlet by the hydrophilizing agent for the hydrophobic porous membrane. Therefore, the hydrophobic porous membrane is gradually hydrophilized from the 2 nd chamber to the 1 st chamber.

(b) When the hydrophilizing agent for the hydrophobic porous membrane is injected from at least 1 or more outlet ports and the remaining hydrophilizing agent for the hydrophobic porous membrane is discharged from the remaining outlet ports, the gas staying in the outlet port and the 2 nd chamber having the outlet port can be pushed out from one outlet port to the other outlet port through the hydrophilizing agent for the hydrophobic porous membrane.

In particular, hollow fiber membrane modules have a complicated structure and are prone to trapping of air bubbles.

When all the inlets and outlets of the membrane module placed in the treatment tank are located above the water surface of the tank and a convection part such as air is hard to appear, the hydrophilizing agent is pushed in from the outlet at a constant pressure and a constant flow rate by using a pump or the like, and air bubbles in the interior of the membrane module can be discharged to fill the entire membrane module with the hydrophilizing agent.

However, when at least one of the water collection sites of the membrane module placed in the treatment tank is located at the lower part of the membrane module, a hydrophilizing liquid is pumped in from the water collection site located at the lower part of the membrane module by a pump or the like, and gas remaining in the piping and the membrane module is pushed out from the water collection site located at the upper part of the membrane module to replace air bubbles with the hydrophilizing agent, whereby the entire membrane module is filled with the hydrophilizing agent.

In addition, while either of the above (a) and (b) can be favorably hydrophilized, the hydrophilizing agent for hydrophobic porous membrane to be injected from all the outlets of (a) is preferable from the viewpoint of simplification of the piping structure at the membrane module outlet in hydrophilization.

In this case, the amount of the hydrophilizing agent for a hydrophobic porous film of the present invention passed through is, for example, 0.3 mass% per 1m when the surfactant concentration is set to²The membrane area is 0.5 to 5 liters, preferably 2 to 3 liters. If the amount of the solution to be passed is 1m per unit²When the membrane area is 0.5 liter or more, a sufficient hydrophilization effect can be obtained. In addition, if the amount of liquid to be passed through is 1m²When the membrane area is 5 liters or less, no extra load is applied to the inside of the membrane separation tank.

The injection rate of the hydrophilizing agent for the hydrophobic porous film is, for example, 0.005 to 3m per unit area of the film³/m²D, preferably in the range of 0.01 to 0.3m³/m²D range. If the injection speed is 3m³/m²D or less, the whole membrane surface can be hydrophilized uniformly, and 0.005m³/m²If D is more than D, the hydrophilization treatment can be carried out quickly.

The rate of adhesion of the hydrophilizing agent for a hydrophobic porous film to the hydrophobic porous film is, for example, 0.01 to 1.0% by mass, preferably 0.05 to 0.5% by mass. The adhesion rate here can be measured as the mass (W) of the hydrophobic porous film before hydrophilization treatment₀) (g) the mass (W) of the hydrophobic porous membrane after hydrophilization treatment and drying₁) (g) using the following formulaObtaining:

(ii) an adhesion rate (%) [ (W)₁(g)-W₀(g))/W₀(g)]×100

When the adhesion rate is 0.01% by mass or more, good hydrophilicity is exhibited, and when it is 1.0% by mass or less, an excessive amount of the hydrophilizing agent for a hydrophobic porous membrane is not contained in the membrane module, and therefore, it is preferable.

The temperature of the hydrophilizing agent for the hydrophobic porous film of the present invention at the time of hydrophilization is, for example, 10 to 50 ℃ and preferably 20 to 30 ℃. When the temperature is 10 ℃ or higher, the hydrophilization rate is not lowered, and the hydrophilization treatment is sufficiently performed, whereby the liquid permeability can be improved. Further, when the temperature is 50 ℃ or lower, the liquid permeability is not lowered by thermal shrinkage or thermal deterioration of the hydrophilizing agent. The time for immersing the hydrophilizing agent for a hydrophobic membrane in the pores is such that the hydrophilizing agent can be recovered immediately after the hydrophobic membrane is injected with the hydrophilizing agent, but at least 30 seconds or more, preferably 10 to 120 minutes, more preferably 30 to 90 minutes, the liquid permeability can be improved by immersing the hydrophobic porous membrane in the hydrophilizing agent for a hydrophobic porous membrane while leaving it still.

After the hydrophilization treatment, the hydrophilizing agent for a hydrophobic porous membrane of the present invention retained in the membrane module can be appropriately recovered by discharging the excess hydrophilizing agent retained in the membrane module by inclining the membrane module or the like. Further, the hydrophilizing agent for a hydrophobic porous film can also be pressed out by passing a liquid or water to be treated from the 1 st chamber having an inlet to the 2 nd chamber having an outlet. This is preferable because the efficiency of hydrophilization of the film can be further improved and the labor for recovery can be reduced. The water used here is preferably pure water or purified water or the like which does not contaminate the clean water in the 2 nd chamber having the outlet. More preferably, the sterilizing liquid may be an aqueous solution of sodium hypochlorite. In addition, the water may be ordinary tap water or ion exchange water filtered through a hollow fiber membrane having a pore diameter of 0.01 to 1 μm.

The method for hydrophilizing a hydrophobic porous film of the present invention will be described in more detail with reference to fig. 1.

Fig. 1 is a schematic view of a membrane separation apparatus including the membrane module of the present invention. The membrane separation apparatus is used for treating a liquid to be treated (liquid to be treated) containing organic substances with microorganisms and a separation membrane. First, a liquid to be treated (3) is introduced into a membrane separation tank (1), and a microbial treatment is performed in the membrane separation tank (1). The organic substances generally include proteins, amino acids, saccharides, lipids and other substances having biodegradability, and if these organic substances are present, they can be effectively removed by microorganisms and the membrane module of the present invention. As the microorganism, a substance contained in activated sludge or the like, or a substance for a bioreactor for producing a usable substance can be used. During the microbial treatment, air is fed into the membrane separation tank (1) from the air diffusion pipe (4). The liquid after the microbial treatment passes through a hydrophobic porous membrane (not shown) in the membrane module (2) to obtain a treated liquid, and is discharged through a pipe (5).

When hydrophilizing the hydrophobic porous membrane of the present invention, first, a hydrophilizing agent for the hydrophobic porous membrane is introduced into the hydrophobic porous membrane (not shown) in the membrane module (2) from the pipe (5) side. When there are a plurality of outlets in the membrane module (2), the remaining hydrophobic porous membrane hydrophilizing agent may be discharged from the membrane separation tank (1) through 1 outlet. Then, the hydrophilizing agent for the hydrophobic porous membrane is retained in the hydrophobic porous membrane for a certain period of time. After a predetermined period of time has elapsed, the clarified water is introduced from the pipe (5) side into the hydrophobic porous membrane (not shown) in the membrane module (2), and the water is replaced with a hydrophilizing agent for the hydrophobic porous membrane. In the replacement, air may be fed from the air diffuser 4 into the membrane separation tank 1. Thus, hydrophilization proceeds, and the concentration of the hydrophilizing agent for the hydrophobic porous film contained in the initial flow of the treatment liquid after the hydrophilization treatment can be appropriately reduced.

By the hydrophilization method of the present invention, i.e., the hydrophilization agent for the hydrophobic porous membrane, which is an aqueous solution of a low-foaming surfactant injected from the treated liquid side, the liquid permeability of the membrane (membrane permeability) can be improved even when at least a part of the hydrophobic porous membrane is driedWhen the amount (flux)) has decreased, the membrane flux can be recovered with a small amount of hydrophilizing agent, amount of work, time, and cost. Furthermore, since a low-foaming surfactant is used, even if a part of the surfactant flows into the membrane separation tank (1) after the hydrophilization treatment and then bubbles up from the gas diffusion pipe (4), foaming by the surfactant can be minimized, and bubbles or the treatment target liquid (3) will not leak out from the membrane separation tank (1). Further, since the hydrophilizing agent for the hydrophobic porous membrane can be replaced with a small amount of water after the hydrophilization treatment, the membrane separation apparatus can be smoothly started by suppressing the contamination of the hydrophilizing agent for the hydrophobic porous membrane into the treated liquid. In addition, in the conventional hydrophilization method using ethanol or the like, the inflow of ethanol into the membrane separation tank (1) causes an increase in the soluble COD in the membrane separation tank (1), and it is difficult to smoothly start the membrane separation apparatus, but the hydrophilizing agent for a hydrophobic porous membrane of the present invention can suppress an increase in the soluble COD in the membrane separation tank (1). The COD can be measured by a known method, for example, by measuring absorbance in accordance with JIS K0102. For example, when the water is present at 0.01m per unit area³/m²When the injection rate of D is within 5 days, preferably within 4 days, the COD value can reach the value before the hydrophilization treatment.

(4) Hydrophilic detection method for membrane module

(4-1) detection method of Membrane Module

Generally, as described above, a membrane module has a main body, an inlet, an outlet, and a porous membrane connected to the inside of the main body, dividing the main body into a 1 st chamber having the inlet and a 2 nd chamber having the outlet. However, if each member such as the body, the inlet, the outlet, and the porous membrane itself or a connection portion between the porous membrane and the inside of the body has a defect (for example, a pinhole, a crack, an incomplete connection, a clogging of the porous membrane, or the like), it cannot function as a good membrane module. Therefore, these defects must be detected.

As a typical product detection Method, a Bubble Point Method (Bubble Point Method) can be given.

This method has been developed for the purpose of evaluating the pore diameter, but is currently widely used for the completeness test of microfiltration membranes or ultrafiltration membranes because of its simplicity, and is defined in JIS K3832 "method for testing the bubble point of microfiltration membrane elements and modules".

The membrane module detection method of the present invention specifically comprises the following steps:

(1) a step of immersing a membrane module in the hydrophilizing agent for a hydrophobic porous membrane of the present invention;

(2) introducing a detection gas from an inlet, passing through the porous hydrophobic film, and discharging the gas from the outlet; and

(3) and observing the air bubbles discharged from the membrane module.

Preferably, the step (2) is carried out as follows:

(i) introducing a gas for detection from the inlet of the membrane module in a state where the outlet is closed,

(ii) the gas for detection is gradually pressurized and,

(iii) water is pushed out from the pores of the hydrophobic porous film by the pressurized detection gas,

(iv) the detection gas passes through the hydrophobic porous membrane and is discharged from the membrane.

If the membrane is damaged or has large pores, air will pass through at a pressure much lower than expected, and the presence of defects on the membrane can be detected.

The hydrophilizing agent for a hydrophobic porous membrane of an impregnated membrane module contains the low-foaming surfactant of the present invention described above and an optional solvent. The detection gas may be introduced immediately after the membrane module is immersed, but it is preferable to immerse the membrane module for a certain period of time because complete hydrophilization can be achieved. The immersion time of the membrane module is, for example, 30 seconds to 30 minutes, preferably 5 to 20 minutes.

As the detection gas, air, an inert gas such as nitrogen or argon, or the like can be used. According to JIS K3832, "method for testing bubble point of microfiltration membrane element and module", detection was carried out by gradually pressurizing detection gas in a range of 5kPa to 1 MPa. Particularly, when a large portion in a process such as a defect in a potting (potting) portion is found, the pressure can be found at a low pressure, and therefore the pressure can be increased within a range of 10 to 100 kPa.

The inspection gas introduced into the membrane module is discharged from the outlet, but the defect detection may be performed on the inlet, the outlet, the main body, and other connecting portions by closing the end of the outlet. Introducing gas for detection into the membrane module, and observing the whole membrane module, the inlet, the outlet and the bubbles released from the main body by eyes; bubbles released from the connection portions of the respective members; hydrophobic porous membrane and air bubbles released from the connection part of the hydrophobic porous membrane and the main body.

Further, when a liquid having a low surface tension is used, since the same defective portion can be detected at a value lower than the pure water measurement pressure, there is an additional effect that the detection can be performed without pressing the membrane module. In this manner, by performing defect detection with the hydrophilizing agent for a hydrophobic porous membrane of the present invention, it is possible to suppress drying and hydrophobization of the hydrophobic porous membrane due to the introduction of a detection gas, and a decrease in liquid permeability due to hydrophobization. This is because, even when the detection gas is introduced, the hydrophobic porous film is spontaneously wetted with water by contact with the hydrophilizing agent for a hydrophobic porous film of the present invention. Further, by using the low foaming surfactant of the present invention, bubbles generated in the defective portion do not stay on the water surface and the defective portion is hardly found. That is, by using the low-foaming surfactant, even if the pressurized gas for detection is introduced into the membrane module, the solution for immersing the membrane module does not foam or foams immediately even if it foams slightly, and thus continuous detection is possible.

Further, problems such as solvent storage, which occur when a hydrophilizing agent such as glycerin, polyethylene glycol, or alcohol is used, can be avoided.

(4-2) method for inspecting and hydrophilizing Membrane Module

After the defect detection is performed by observing the bubbles, the following steps may be further performed:

(4) the membrane module may be subjected to a hydrophilization treatment by a step of drying the membrane module. The hydrophilization treatment is mainly carried out by immersing the membrane module of the above step (1) in the hydrophilizing agent for a hydrophobic porous membrane of the present invention, but then drying the membrane module in the above step (4) allows the product in which the surface of the hydrophobic porous membrane is hydrophilized and kept in a dry state to flow, and allows the membrane module product to pass through the liquid to be treated with high liquid permeability without further hydrophilization treatment at the time of use, and further, allows the initial flow of the treated liquid recovered as a waste liquid to be reduced as much as possible. Further, since the hydrophilizing agent for a hydrophobic porous film of the present invention has low foaming properties, the above-described defect detection and hydrophilization treatment can be performed simultaneously.

The drying temperature after the defect detection is, for example, 20 to 120 ℃, preferably 30 to 60 ℃. When the drying temperature is 20 ℃ or higher, a sufficiently high liquid permeability can be provided, and when the drying temperature is 120 ℃ or lower, the heat shrinkage of the hydrophobic porous film and the decrease in liquid permeability due to the thermal deterioration of the hydrophilizing agent for a hydrophobic porous film of the present invention can be suppressed.

Examples

[ example 1]

As the hydrophilizing agent for a hydrophobic porous film of the present invention, an aqueous solution (static surface tension of 25.8mN/m, 27.1mN/m in terms of the static surface tension of a 0.1% by mass aqueous solution) containing 0.3% by mass of an alkyne vicinal diol surfactant (Olfinex 4036 (manufactured by Nikkiso chemical industries Co., Ltd.) was used.

Comparative example 1

As the hydrophilizing agent, a 40 mass% glycerol aqueous solution (containing 15 mass% EtOH) was used.

Comparative example 2

As the hydrophilizing agent, a 1.0 mass% aqueous solution of a higher alcohol ether type nonionic surfactant Emulgen LS-106 (manufactured by Kao corporation: surface tension 29.5mN/m) was used.

Comparative example 3

As the hydrophilizing agent, a 30% aqueous solution of ethanol (and 99.5% of Wako pure chemical industries, Ltd.) was used.

[ porous film 1]

The pure water permeability coefficient was set to 100m³/m²A membrane comprising a hollow fiber membrane (manufactured by Mitsubishi corporation) made of vinylidene fluoride resin having an outer diameter of 2.4mm and a pore diameter of 0.4 μm as a hydrophobic porous membrane.

[ porous film 2]

The pure water permeability coefficient was set to 30m³/m²A film comprising a hollow fiber membrane (manufactured by Mitsubishi corporation) made of a polyethylene resin having an outer diameter of 0.54mm and a pore diameter of 0.4 μm/hr/MPa as a hydrophobic porous membrane.

[ Membrane module ]

A plurality of the porous membranes 1 were bundled together to prepare a membrane having a membrane area of 4.4m²The membrane module of (1).

(1) Foaming test

The hydrophilizing agent for hydrophobic porous film of example 1 was subjected to foaming test by the Rossemules method. The test was carried out according to JIS K3362. Water was further added to the aqueous solution of the hydrophilizing agent for hydrophobic porous membrane of example 1 to prepare an aqueous solution of 0.1 mass%. Then, the foam height immediately after foaming and after 5 minutes of foaming was measured at 25 ℃.

The foaming property test of the surfactant of comparative example 2 was also performed according to the rossmills method as described above.

The results are shown in table 1 below.

[ Table 1]

	Bubble height immediately after bubbling	Height of foam after 5 minutes of foaming
			Example 1	25mm	≤10mm
Comparative example 2	87mm	48mm

(2) Defect detection

[ test 1] the porous membrane 1 was immersed in the hydrophilizing agent for a hydrophobic porous membrane of example 1 for 10 minutes, and then pressurized air (50kPa) was introduced from the inlet of the membrane module to plug and seal the outlet and the inlet. Bubbles appear in the defect part of the membrane assembly, but the generated bubbles disappear immediately, the defect finding is not influenced, and the defect product detection is easy to continue.

[ detection 2] the membrane module was detected in the same manner as in detection 1 except that the porous membrane 2 was used instead of the porous membrane 1. Bubbles appear in the defect part of the membrane assembly, but the generated bubbles disappear immediately, the defect finding is not influenced, and the defect product detection is easy to continue.

Comparative test 1 the membrane module was tested in the same manner as in test 1 except that the surfactant of comparative example 2 was immersed for 30 minutes instead of being immersed for 10 minutes in the hydrophilizing agent for hydrophobic porous membrane of example 1. Bubbles appear in the defect part of the membrane component, bubbles appear on the water surface, and the bubbles remain on the water surface and are difficult to disappear. And thus defect detection is difficult.

(3) Hydrophilicity and COD test

[ test 1] the defect-free porous membrane 1 was immersed in the hydrophilizing agent for the hydrophobic porous membrane of example 1 for 10 minutes to carry out hydrophilization treatment. Then, the porous membrane 1 was dried at 50 ℃ for 4 hours, and the pure water permeability coefficient was measured in water. The pure water permeability coefficient can be obtained by the following equation:

pure water permeability coefficient [ pure water permeability (m)³)]/[ surface area of porous film (m)²)]/[ permeation time (hr)]/[ pressure of pure Water (MPa)]

In addition, in order to measure the elution amount of the hydrophilizing agent for the hydrophobic porous membrane from the hydrophobic porous membrane, the membrane module was passed through water under a water passage pressure of 0.1MPa, and the COD in the membrane-filtered water 30 minutes after the start of the water passage was determined_MnThe value is obtained. COD in the present invention_MnThe value can be measured according to JIS method (JIS K0102) using COD of absorbance formula_MnValue measurement kit (CKC (Central Kagaku)).

[ test 2] the defect-free porous membrane 2 was immersed in the hydrophilizing agent for the hydrophobic porous membrane of example 1 for 10 minutes to carry out hydrophilization treatment. Then, the porous membrane 1 was dried at 50 ℃ for 4 hours, and the pure water permeability coefficient was measured in water.

Comparative test 1A porous membrane 1 having no defects and not subjected to hydrophilization treatment was dried at 50 ℃ for 4 hours, and then the pure water permeability was measured in water

[ comparative experiment 2]The defect-free porous membrane 1 was immersed in 40 mass% of comparative example 1The hydrophilization treatment was carried out in an aqueous glycerol solution for 10 seconds. Then, the porous membrane 1 was dried at 50 ℃ for 4 hours in the same manner as in test 1, and the pure water permeability was measured in water. Furthermore, COD was measured 30 minutes after the water passing pressure of 0.1MPa was applied to the membrane module and water passing was started_MnThe value is obtained.

Comparative test 3 the defect-free porous membrane 1 was immersed in the surfactant aqueous solution of comparative example 2 for 10 minutes to be subjected to hydrophilization treatment. Then, the porous membrane 1 was dried at 50 ℃ for 4 hours in the same manner as in test 1, and the pure water permeability was measured in water.

These results are shown in table 2 below.

[ Table 2]

Tests 1 and 2 showed pure water permeability coefficients of the same degree as those in the case of hydrophilization and water substitution with ethanol (30% aqueous solution). However, in comparative test 2, the amount of glycerin eluted was large.

(4) Hydrophilization test of hydrophobic porous membrane of membrane separation device

[ test 3]

At a height of 0.7m³The membrane separation tank (1) of the membrane separation device of the membrane separation tank (1) is filled with general domestic wastewater which has been subjected to a pretreatment such as coagulation and precipitation as a liquid to be treated (3). Activated sludge as a microorganism is added to the membrane separation tank (1).

A membrane module (2) is immersed and installed in the membrane separation tank (1) at a rate of 1m per unit²2 liters of membrane area, 0.01m per unit membrane area³/m²D, the hydrophilizing agent for the hydrophobic porous membrane of example 1 was injected into the membrane module (2) from the pipe (5). After the completion of the injection, the mixture was left to stand for 60 minutes to carry out hydrophilization treatment. At a rate of 1m²2 liters of membrane area, 0.01m per unit membrane area³/m²D injection rate Water filtered through a hollow fiber membrane (pore diameter: 0.1 μm) was injected from a pipe (5) into the membrane module (2), and the hydrophilizing agent for the hydrophobic porous membrane of example 1 was pushed into the membrane separation tank (1). Immediately after the completion of the hydrophilization treatment, the membrane separation apparatus is started by introducing air from the air diffusion pipe (4) and discharging the treated liquid from the pipe (5). The pure water permeability of the hydrophobic porous membrane and the COD of the treated liquid were measured for the next 1 week_MnThe value is obtained.

The results are shown in table 3 below.

[ Table 3]

Test 3	Pure water permeability coefficient (m)/m/hr/MPa)	CODValue (mg/l)
			Before hydrophilization	100	12.0
After 0 minute	98	89.3
			After 1 hour	100	16.3
After 24 hours	99	13.6
			After 2 days	100	13.5
After 3 days	97	12.3
			After 4 days	100	11.8
After 5 days	100	11.8
			After 6 days	100	12.0
After 7 days	97	11.3

The pure water permeability was not drastically decreased in 1 week after the hydrophilization treatment, and it was confirmed that the hydrophilization treatment was sufficiently performed. In addition, the treated liquid (3) does not foam, bubbles and treated liquid (3) overflow the membrane separation tank (1) because air is filled from the air dispersion pipe (4), and the hydrophilization treatment can be immediately and smoothly started.

15, compared with before hydrophilization treatmentCOD of treated liquor of initial flow after minute_MnThe value is increased by about 4mg/l, but after 24 hours from the start of the start, the COD is_MnThe value was reduced to the same level as before the hydrophilization treatment.

[ comparative test 4]

The pure water permeability of the hydrophobic porous membrane and the COD of the treated liquid were measured in the same manner as in test 3, except that the 40 mass% glycerol aqueous solution of comparative example 1 was injected from the pipe (5) into the membrane module (2)_MnThe value is obtained.

The results are shown in Table 4 below.

[ Table 4]

Comparative experiment 4	Pure water permeability coefficient (m)/m/hr/MPa)	CODValue (mg/l)
			Before hydrophilization	100	11
After 0 minute	98	15700
			After 1 hour	100	2200
After 24 hours	99	450
			After 2 days	100	120
After 3 days	97	70
			After 4 days	100	35
After 5 days	100	18
			After 6 days	100	12.5
After 7 days	97	11.0

COD of the treated liquid at the initial flow after 1 hour compared with that before the hydrophilization treatment_MnThe value increased by around 2189 mg/l. The treated liquid at the start of the startup had to be used as a waste liquid, including the initial flow. Even 24 hours after the start of the activation, the concentration was higher than that before the hydrophilization treatment, and after about 5 days, COD was observed_MnThe value dropped to the same level as before the plunge.

[ comparative test 5]

The pure water permeability of the hydrophobic porous membrane and the COD of the treated liquid were measured in the same manner as in test 3 except that the aqueous ethanol solution of comparative example 3 was injected into the membrane module (2) through the pipe (5)_MnThe value is obtained.

The results are shown in Table 5 below.

[ Table 5]

Comparative experiment 5	Pure water permeability coefficient (m)/m/hr/MPa)	CODValue (mg/l)
			Before hydrophilization	100	12.0
After 0 minute	98	1942.0
			After 1 hour	100	105.8
After 24 hours	99	20.5
			After 2 days	99	14.5
After 3 days	97	13.8
			After 4 days	96.5	12.0
After 5 days	94.8	11.8
			After 6 days	95.3	12.0
After 7 days	94.8	12.3

The pure water permeability did not decrease rapidly 1 week after the hydrophilization treatment, and it was confirmed that the hydrophilization treatment was sufficiently sufficient. In addition, air is filled from the air diffusing pipe (4), the liquid (3) to be treated slightly foams, but the air bubbles and the liquid (3) to be treated do not overflow out of the membrane separation tank (1), and the hydrophilization treatment can be immediately and smoothly carried out.

COD of the treated liquid at the initial flow after 0 minute compared with that before the hydrophilization treatment_MnThe value increased by about 1830mg/l, so that the treated liquid had to be used as a waste liquid. The ethanol is biodegraded for about 1 dayThe device cannot be activated immediately after the hydrophilization treatment.

Claims (5)

1. A hydrophilizing agent for a hydrophobic porous film, characterized by comprising a surfactant which is an vicinal alkyne diol, an ethoxylate of the vicinal alkyne diol, or a mixture thereof, and which has a foaming property such that a foam height immediately after foaming of a 0.1 mass% aqueous solution of the surfactant measured at 25 ℃ according to Ross-miles method of JIS K3362 is 40mm or less.

2. A method for hydrophilizing a hydrophobic porous film, comprising the step of contacting the hydrophobic porous film with the hydrophilizing agent for hydrophobic porous film according to claim 1.

3. The method for hydrophilizing a hydrophobic porous film according to claim 2, further comprising the step of drying the hydrophobic porous film which has been contacted with the hydrophilizing agent for a hydrophobic porous film according to claim 1.

4. A membrane module detection method comprising a main body, an inlet and an outlet provided in the main body, and a hydrophobic porous membrane provided in the main body, the method comprising the steps of:

(1) a step of immersing the membrane module in the hydrophilizing agent for a hydrophobic porous membrane according to claim 1;

(2) introducing a detection gas from the inlet, passing through the porous hydrophobic film, and discharging the gas from the outlet; and

(3) and observing the air bubbles discharged from the membrane module.

5. A method for testing and hydrophilizing a membrane module having a main body, an inlet and an outlet provided in the main body, and a hydrophobic porous membrane provided in the main body, the method comprising the steps of:

(1) a step of immersing the membrane module in the hydrophilizing agent for a hydrophobic porous membrane according to claim 1;

(2) introducing a detection gas from the inlet, passing the detection gas through the porous hydrophobic membrane, and discharging the detection gas from the outlet;

(3) observing the gas bubbles discharged from the membrane module; and

(4) and drying the membrane module.